[92GTA]

So the rocker stud nuts for the #1 cylinder on my 461 loosened. I got lucky and made it home; the pushrod was straight, the rocker and ball were on the stud shifted over and off the pushrod dangling, and the top nut was right there under the valve cover, the adjustment nut at the top of the stud. Looked everything over, zero damage. Totally dodged that one.

I'm not sure why a professional engine builder would have not used poly locks and simply used 2 nuts instead, but they did. Seems like an accident waiting to happen to me. They aren't locking nuts, just plan jane nuts.

What's a good way to avoid this in the future? Looking at Butler's poly lock kits I have to replace the studs, which I don't want to do. I'm running a Comp hydraulic flat tappet cam.

Thanks!

[ta man]

You can use crimp nuts.

[92GTA]

Originally Posted by ta man

You can use crimp nuts.

Hmm, never heard of a crimp nut. I'll Google that, thanks!

[AG]

I think I have locknuts for stock 3/8" rocker studs if you are interested.

[92GTA]

Originally Posted by AG

I think I have locknuts for stock 3/8" rocker studs if you are interested.

That should work, I have rebuild 670 heads that should be 3/8 at the rocker threads. I'll PM you.


I didn't have much luck searching for crimp nuts for rocker studs or the like.

[ta man]

Originally Posted by 92GTA

Hmm, never heard of a crimp nut. I'll Google that, thanks!

AKA locknuts.

[92GTA]

Ah, gotcha. Thanks!

[b-man]

I’d be replacing those weak bottleneck studs with some ARP straight 7/16” studs and run some 7/16” polylocks.

Those factory studs are prone to breakage, down the road you’ll be glad you did.

Yes it’s more money and work but it’s the right way. Too bad that your builder doesn’t know about this essential valvetrain upgrade. A breakdown out on road will be prevented by doing it right, the stock studs are only good for stock engines.

The 3/8” crimp nuts are for SBC, 7/16” for BBC if you decide to go that route. Keep in mind those Chevy crimp nuts aren’t meant for multiple adjust cycles.

[92GTA]

The car's previous owners chose the engine builder.

Good point on the ARP studs, I just checked my receipts and it looks like they did use ARP: "7/16 Rocker Arm Stud 1.750" Black Oxide Coating"

So I need these? https://www.ebay.com/itm/133759682721

Or since I already have those ARP studs, can I go with poly locks now?

Thanks for the info!

[sdbob]

I also would use 7/16. Also someone years ago maybe 40 told me to file flat the top of the stud before using the poly lock nut with set screw, to get a flat service for the allen set screw to grab. I cant say I've had any issues but I'm not turning 6500 rpms. Maybe 6200 at most.

[77 TRASHCAN]

There are 2 types of crimp nuts. The top of one style tapers with the top of the nut like a pop bottle. When they are new. You can see the the bottleneck is not round, but IS threaded. The misf[rmef top is what males it a "lock" nut. If this style of nut losses it's locking ability, you can re-crimp the top by putting the top of the nut in a vice, and retightening the crimp. I have only seen these type of lock nuts on small block Chevrolets. I believe they are aftermarket.

The other type of locking rocker nuts look like the picture you posted (those look like lugs nuts the picture is a little fuzzy. On my phone). This type of locking rocker nut DOES look like a common tapered seat lug nut, with the taper facing up, but they are not intetchageable.interchangeable. generally there are 3 stamped "triangles" on the tapered top of the nut. These locking rocker nuts are crimped on the top in 3 equally spaced spots. These can also be re- crimped with a center punch. I have seen these on small and big block Chevys.

The double nuts on your engine. Should work, but sound home made. Grade 8 nuts would be only way to go. If you decide to keep this setup.

[Joe's Garage]

With the ARP studs already there, you're good-to-go on polylocks.

You may want to get one of the shorter-styles and make sure you double-check your clearance to the valve covers.

https://www.summitracing.com/parts/cro-86050s-16

We've used double Ram Air IV cork valve cover gaskets (5/16" x 2) to add clearance when needed.

They also make valve cover spacers in various thicknesses, but your clearance to your brake booster can come into play.

Good luck!

[Formulas]

Stover is another name for crimp lock nuts,
nuts are nice with a solid cam easier to get lash
but poly locs are great for juice lifters

[NeighborsComplaint]

Originally Posted by 92GTA

Hmm, never heard of a crimp nut. I'll Google that, thanks!

They are a nut that is flattened to be slightly out of round. You tighten them down and the stud cuts new threads while forcing them back into a round condition, keeping them tight. However, they are considered a one-time use only. Once you have cranked them down, if you loosened them and retighten, they no longer lock by interference as you have fully re-cut new threads.

Poly-loks are the best for maintaining your adjustments but there is no reason a standard nut with a thin jam nut added like I assume you had (old school way of locking valve lash on solid lifter cars) won't hold adjustment either ... if they are tightened properly.

[Sirrotica]

FWIW, the OEM RA IV did consist of a 2 nut system with conventional nuts locking against each other. They also came with 7/16 inch studs. Being difficult to adjust, the system was usually replaced quickly with BBC lock nuts, or 7/16 inch poly locks. If memory serves, one of the nuts was conventional sized, and the other was thinner, about half the thickness.

It's a possibility the guy used a discarded 2 nut jamb system from a RA IV that had been substituted with the aforementioned locking nuts.

[Tom Vaught]

Originally Posted by b-man

I’d be replacing those weak bottleneck studs with some ARP straight 7/16” studs and run some 7/16” polylocks.

Those factory studs are prone to breakage, down the road you’ll be glad you did.

Yes it’s more money and work but it’s the right way. Too bad that your builder doesn’t know about this essential valvetrain upgrade. A breakdown out on road will be prevented by doing it right, the stock studs are only good for stock engines.

The 3/8” crimp nuts are for SBC, 7/16” for BBC if you decide to go that route. Keep in mind those Chevy crimp nuts aren’t meant for multiple adjust cycles.

X2 Tom V.

[b-man]